This invention relates generally to a wire guide used to position a catheter or other medical tool at a precise location within a patient. In particular, this invention relates to a small-diameter wire guide which can be steered into and along very narrow blood vessels to locate its distal end in a precise position.
In order to negotiate a tortuous path or avoid obstacles during an insertion, wire guides frequently include a floppy tip that is often biased in a certain direction. However, it is desirable that the remaining portion of the wire guide be somewhat elastic and resistant to kinking but still able to transmit a torque so that the physician can reliably change the direction of the bias tip to make a turn or avoid an obstacle while advancing the wire guide into position. It has been found that using a superelastic material (sometimes expressed as "pseudoelastic"), such as a nickel titanium alloy, in the body of the wire guide has significant advantages over conventional steel wire guides, in that nitinol's superelastic properties can allow physicians to reach much more remote locations within the body. In other words, wire guides made of certain nickel titanium alloys simply have improved torque control and more resistance to kinking than conventional stainless steel.
What is needed is an extremely small-diameter wire guide which has improved torque control over conventional stainless steel wire guides, has substantial kink-resistance over the majority of its length, has a distal region of gradual-increasing flexibility and includes an extremely flexible radiopaque distal coil tip.